For many years, petroleum products have been recovered from subterranean reservoirs through the use of drilled wells and production equipment. During the production of desirable hydrocarbons, such as crude oil and natural gas, a number of other naturally occurring substances may also be encountered within the subterranean environment.
For example, hydrogen sulfide (H2S) is a highly toxic, colorless gas that is produced during the decomposition of organic matter. In some areas, hydrogen sulfide gas is produced in large quantities during the retrieval of petroleum products. At relatively low concentrations (200 ppm) and minimal exposure times, hydrogen sulfide gas can be lethal. In areas prone to the production of hydrogen sulfide, drilling crews must be prepared to use detection and protective equipment at all times. The contamination of well sites from hydrogen sulfide gas is a significant environmental concern that requires extensive remediation. Additionally, during downstream processing, hydrogen sulfide is typically removed from refined products through expensive and waste-extensive procedures. The control and mitigation of hydrogen sulfide is a significant business that is strictly regulated throughout petroleum producing countries.
In addition to hydrogen sulfide, other undesirable downhole products must be managed during the production of hydrocarbons. For example, scale, paraffins, fines, sulfur, heavy oil tar by-products and water blocks commonly accumulate in and around the formation, well casing, production tubing and recovery equipment. Alternatively, it may be necessary to remove injected fluids from the near wellbore area, such as drilling fluids, cement filtrate, kill fluids, polymers and water blocks. To maintain an efficient recovery of petroleum products, it is frequently necessary to clean or remove these accumulations and deposits.
The removal of unwanted deposits from the wellbore and production equipment is generally referred to as “remediation”. In contrast, the term “stimulation” generally refers to the treatment of geological formations to improve the recovery of hydrocarbons. Common stimulation techniques include well fracturing and acidizing operations. Well remediation and stimulation are important services that are offered through a variety of techniques by a large number of companies.
Although a number of compounds and techniques are known in the prior art, there is a continued need for more effective methods and compounds for hydrogen sulfide mitigation, wellbore remediation, drilling operations and formation stimulation.